In the following example I am looking to include the * metacharacter in the string replacement. If I understand correctly, I should be able to escape the character using \ but after doing that this is the result I am seeing:
❯ echo 'foo(*)' | sed s/foo\(\*/bar/g
bar*)
I was expecting to see the following:
❯ echo 'foo(*)' | sed s/foo\(\*/bar/g
bar)
You need to quote your sed command:
echo 'foo(*)' | sed 's/foo(\*/bar/g'
bar)
Related
I am trying to separate out parts of a path as follows. My input path takes the following possible forms:
bucket
bucket/dir1
bucket/dir1/dir2
bucket/dir1/dir2/dir3
...
I want to separate the first part of the path (bucket) from the rest of the string if present (dir1/dir2/dir3/...), and store both in separate variables.
The following gives me something close to what I want:
❯ BUCKET=$(echo "bucket/dir1/dir2" | sed 's#\(^[^\/]*\)[\/]\(.*\)#\1#')
❯ EXTENS=$(echo "bucket/dir1/dir2" | sed 's#\(^[^\/]*\)[\/]\(.*\)#\2#')
echo $BUCKET $EXTENS
❯ bucket dir1/dir2
HOWEVER, it fails if I only have bucket as input (without a slash):
❯ BUCKET=$(echo "bucket" | sed 's#\(^[^\/]*\)[\/]\(.*\)#\1#')
❯ EXTENS=$(echo "bucket" | sed 's#\(^[^\/]*\)[\/]\(.*\)#\2#')
echo $BUCKET $EXTENS
❯ bucket bucket
... because, in the absence of the first '/', no capture happens, so no substitution takes place. When the input is just 'bucket' I would like $EXTENS to be set to the empty string "".
Thanks!
For something so simple you could use bash built-in instead of launching sed:
$ path="bucket/dir1/dir2"
$ bucket="${path%%/*}"
$ extens="${path#$bucket}"
$ printf '|%s|%s|\n' "$bucket" "$extens"
|bucket|/dir1/dir2|
$ path="bucket"
$ bucket="${path%%/*}"
$ extens="${path#$bucket}"
$ printf '|%s|%s|\n' "$bucket" "$extens"
|bucket||
But if you really want to use sed and capture groups:
$ declare -a bucket_extens
$ mapfile -td '' bucket_extens < <(printf '%s' "bucket/dir1/dir2" | sed -E 's!([^/]*)(.*)!\1\x00\2!')
$ printf '|%s|%s|\n' "${bucket_extens[#]}"
|bucket|/dir1/dir2|
$ mapfile -td '' bucket_extens < <(printf '%s' "bucket" | sed -E 's!([^/]*)(.*)!\1\x00\2!')
$ printf '|%s|%s|\n' "${bucket_extens[#]}"
|bucket||
We use the extended regex (-E) to simplify a bit, and ! as separator of the substitute command. The first capture group is simply anything not containing a slash and the second is everything else, including nothing if there's nothing else.
In the replacement string we separate the two capture groups with a NUL character (\x00). We then use mapfile to assign the result to bash array bucket_extens.
The NUL trick is a way to deal with file names containing spaces, newlines... NUL is the only character that cannot be part of a file name. The -d '' option of mapfile indicates that the lines to map are separated by NUL instead of the default newline.
Don't capture anything. Instead, just match what you don't want and replace it with nothing:
BUCKET=$(echo "bucket" | sed 's#/.*##'). # bucket
BUCKET=$(echo "bucket/dir1/dir2" | sed 's#/.*##') # bucket
EXTENS=$(echo "bucket" | sed 's#[^/]*##') # blank
EXTENS=$(echo "bucket/dir1/dir2" | sed 's#[^/]*##') # /dir1/dir2
As you are putting a slash in the regex. the string with no slashes will not
match. Let's make the slash optional as /\?. (A backslash before ?
is requires due to the sed BRE.) Then would you please try:
#!/bin/bash
#path="bucket/dir1/dir2"
path="bucket"
bucket=$(echo "$path" | sed 's#\(^[^/]*\)/\?\(.*\)#\1#')
extens=$(echo "$path" | sed 's#\(^[^/]*\)/\?\(.*\)#\2#')
echo "$bucket" "$extens"
You don't need to prepend a backslash to a slash.
By convention, it is recommended to use lower cases for user variables.
How do you escape line beginning and line end in bracket expressions in sed?
For example, let's say I want to replace both comma, line beginning, and line end in each line with pipe:
echo "a,b,c" | sed 's/,/|/g'
# a|b|c
echo "a,b,c" | sed 's/^/|/g'
# |a,b,c
echo "a,b,c" | sed 's/$/|/g'
# a,b,c|
echo "a,b,c" | sed 's/[,^$]/|/g'
# a|b|c
I would expect the last command to produce |a|b|c|. I also tried escaping the line beginning and line end via backslash, with no change.
With GNU sed with extended regular expressions, you can do:
$ echo "a,b,c" | /opt/gnu/bin/sed -E 's/^|,|$/|/g'
|a|b|c|
$
The -E option enables the extended regular expressions, as does -r, but -E is also used by other sed variants for the same purpose, unlike -r.
However, for reasons which elude me, the BSD (macOS) variant of sed produces:
$ echo "a,b,c" | sed -E 's/^|,|$/|/g'
|a|b|c
$
I can't think why.
If this variability is unacceptable, go with the three-substitution solution:
$ echo "a,b,c" | sed -e "s/^/|/" -e "s/$/|/" -e "s/,/|/g"
|a|b|c|
$
which should work with any variant of sed. However, note that echo "" | sed …3 subs… produces || whereas the -E variant produces |. I'm not sure if there's an easy fix for that.
You tried this, but it didn't do what you wanted:
$ echo "a,b,c" | sed 's/[,^$]/|/g'
a|b|c
$
This is what should be expected. Inside character classes, most special characters lose their special-ness. There is nothing special about $ (or , but it isn't a metacharacter anyway) in a character class; ^ is only special at the start of the class and it negates the character class. That means that what follows shows the correct, expected behaviour from this permutation of the contents of your character class:
$ echo "a,b\$\$b,c" | sed 's/[^,$]/|/g'
|,|$$|,|
$
It mapped all the non-comma, non-dollar characters to pipes. I should be using single quotes around the echo; then the backslashes wouldn't be necessary. I just followed the question's code quietly.
Following sed may help you in same.
echo "a,b,c" | sed 's/^/|/;s/,/|/g;s/$/|/'
Output will be as follows.
|a|b|c|
I need a sed command to replace a line in config file that contains /.
I want to change /var/log/haproxy to /root/myDir/haproxy in the file.
Can you please help? Thanks in advance.
If you want to replace a string containing slashes, just use a different delimiter for the sed expression:
sed 's#/var/log/haproxy#/root/myDir/haproxy#g' <file>
Here's an example:
$ echo /var/log/haproxy | sed 's#/var/log/haproxy#/root/myDir/haproxy#g'
/root/myDir/haproxy
sed will automatically use whatever character follows the s as the delimiter. These will also work:
$ echo /var/log/haproxy | sed 's#/var/log/haproxy#/root/myDir/haproxy#g'
/root/myDir/haproxy
$ echo /var/log/haproxy | sed 's^/var/log/haproxy^/root/myDir/haproxy^g'
/root/myDir/haproxy
$ echo /var/log/haproxy | sed 's%/var/log/haproxy%/root/myDir/haproxy%g'
/root/myDir/haproxy
You can also just escape the /'s in the path and keep using /, but that's harder to read, so I don't recommend it:
$ echo /var/log/haproxy | sed 's/\/var\/log\/haproxy/\/root\/myDir\/haproxy/g'
/root/myDir/haproxy
How do I remove the first and the last quotes?
echo "\"test\"" | sed 's/"//' | sed 's/"$//'
The above is working as expected, But I guess there must be a better way.
You can combine the sed calls into one:
echo "\"test\"" | sed 's/"//;s/"$//'
The command you posted will remove the first quote even if it's not at the beginning of the line. If you want to make sure that it's only done if it is at the beginning, then you can anchor it like this:
echo "\"test\"" | sed 's/^"//;s/"$//'
Some versions of sed don't like multiple commands separated by semicolons. For them you can do this (it also works in the ones that accept semicolons):
echo "\"test\"" | sed -e 's/^"//' -e 's/"$//'
Maybe you prefer something like this:
echo '"test"' | sed 's/^"\(.*\)"$/\1/'
if you are sure there are no other quotes besides the first and last, just use /g modifier
$ echo "\"test\"" | sed 's/"//g'
test
If you have Ruby(1.9+)
$ echo $s
blah"te"st"test
$ echo $s | ruby -e 's=gets.split("\"");print "#{s[0]}#{s[1..-2].join("\"")+s[-1]}"'
blahte"sttest
Note the 2nd example the first and last quotes which may not be exactly at the first and last positions.
example with more quotes
$ s='bl"ah"te"st"tes"t'
$ echo $s | ruby -e 's=gets.split("\"");print "#{s[0]}#{s[1..-2].join("\"")+s[-1]}"'
blah"te"st"test
Sometime we have problem with the file PATH syntax
For example
Wrong PATH as (double back slash)
/etc//sysconfig/network
While the right syntax is
/etc/sysconfig/network
How to fix by sed if the PATH have two double spaces (consecutive)
For example
echo /etc//sysconfig/network | sed …
will print
/etc/sysconfig/network
just use the shell(bash)
$ path="/etc//sysconfig/network"
$ echo ${path//\/\//\/}
/etc/sysconfig/network
otherwise, if you still prefer sed
$ echo "$path" | sed 's/\/\//\//g'
/etc/sysconfig/network
The following looks like a sine wave but it does the trick:
pax> echo /etc//sysconfig/network | sed 's/\/\/*/\//g'
/etc/sysconfig/network
It works by collapsing all occurrences of two or more / characters into a single one.